1. Field of the Invention
The present invention relates to a honeycomb structure.
2. Discussion of the Background
In recent years, particulate matter (hereinafter, also referred to as PM) such as soot contained in exhaust gases discharged from internal combustion engines of vehicles such as buses and trucks, construction machines and the like, and other harmful contaminants have raised serious problems to the environment and the human body.
For this reason, various porous ceramic honeycomb structured bodies have been proposed as filters that capture PM in exhaust gases and purify the exhaust gases and also as catalyst supporting carriers that convert contaminants in exhaust gases by allowing the exhaust gases to pass through the inside of the catalyst supporting carriers.
With respect to such a honeycomb structure, there has been known an aggregated honeycomb structure formed by combining a plurality of pillar-shaped honeycomb fired bodies each having a large number of cells longitudinally placed in parallel with one another. In such an aggregated honeycomb structure, an adhesive layer is formed on each of side faces of the honeycomb fired bodies, and the respective honeycomb fired bodies are bonded to one another with the adhesive layer interposed therebetween.
Upon use of a honeycomb structure for purifying or converting exhaust gases, the honeycomb structure allows high-temperature exhaust gases to flow through cells of the honeycomb structure. Consequently, a thermal shock is applied to the honeycomb structure during use, and when the thermal shock is increased, the honeycomb structure tends to be damaged.
However, by combining honeycomb fired bodies with one another with an adhesive layer interposed therebetween to form an aggregated honeycomb structure, the thermal shock applied to the honeycomb structure is alleviated by the adhesive layer so that it is possible to prevent the damage in the honeycomb structure.
WO 97/25203 A1 has described a honeycomb structure including a plurality of honeycomb fired bodies combined by using an adhesive containing inorganic particles, inorganic fibers, an inorganic binder and an organic binder, as an aggregated honeycomb structure.
Moreover, WO 03/067041 A1 has described a honeycomb structure in which pores are formed in an adhesive layer by adding a pore-forming agent to the adhesive layer to adjust the porosity of the adhesive layer.
The contents of WO 97/25203 A1 and WO 03/067041 A1 are incorporated herein by reference in their entirety.